Method and apparatus for supplying low voltage current to low voltage spark plugs, more particularly for an ignition device for internal combustion engines



June 21, 1955 W. B. SMITS METHOD AND APPARATUS FOR SUPPLYING LOW VOLTAGE CURRENT TO LOW VOLTAGE SPARK PLUGS, MORE PARTICULARLY FOR -AN IGNITION DEVICE FOR INTERNAL COMBUSTION ENGINES Filed June 6, 1950 4 Sheets-Sheet l \izgr HE w INVENTOR W/JTZE BEYE 8/4/715,

ATTORNEY June 21, 1955 w w. B. SMITS 2,711,495

METHOD AND APPARATUS FOR SUPPLYING LOW VOLTAGE CURRENT TO LOW VOLTAGE SPARK PLUGS, MORE PARTICULARLY FOR AN IGNITION DEVICE FOR INTERNAL COMBUSTION ENGINES I Filed June 6, 1950 4 Sheets-Sheet 2 kiz'g kwiz'y. 6.

INVENTOR W/JTZE BEY' 361/73,

ATTORNEY June 21, 1955 w 5M|T$ 2,711,495

METHOD AND APPARATUS FOR SUPPLYING LOW VOLTAGE CURRENT TO LOW VOLTAGE SPARK PLUGS, MORE PARTICULARLY FOR AN IGNITION DEVICE FOR INTERNAL COMBUSTION ENGINES Filed June 6, 1950 4 Sheets-Sheet 3 INVENTOR W/J T25 55 YE ism/725,

ATTORNEY June 21, 1955 W. B. SMITS METHOD AND APPARATUS FOR SUPPLYING LOW VOLTAGE CURRENT TO LOW VOLTAGE SPARK PLUGS, MORE PARTICULARLY FOR AN E FOR INTERNAL COMBUSTION ENGINES IGNITION DEVIC Filed June 6, 1950 4 Sheets-Sheet 4 INVENTOR W/./ 72.5 55y: \EM/TS,

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'ATTORNEY United States Patent Wytze Beye Smits, Veer-burg, Netherlands, assignor t0 Smitsvonk N. V., Rijswiik, Netherlands, a corporation of the Netherlands Application June 6, 1950, Serial No. 166,472

1 Claim. (Cl. 315-183) The present invention relates to a method and apparatus for supplying low voltage current to low volt-- age spark plugs and-is particularly suitable for use in an ignition system of internal combustion engines or the like.

The use of the low voltage so-called flush gap plugs operating from aperiodic or substantially aperiodic condenser discharge currents, enables the use of low voltage current supplying devices, more particularly for application to the ignition systems of internal combustion engines or in other devices in which inflammable or explosive substances are being ignited by means of an electric discharge. In this way, according to this invention, it has become possible to build lighter, smaller and less expensive ignition systems which, owing to their simplicity and the absence of rapidly burning or wearing out of parts together with the use of voltages which are considerably lower than those used hitherto, have a long life and great reliability.

As a special advantage it may be mentioned that the use of the interrupter for determining the moment of ignition and which is connected in the primary circuit in previous forms of ignition devices is rendered superfiuous by this invention.

It is known that in the conventional ignition systems the correct operation depends in a very high degree on the interrupter. The interrupter, therefore, is an essential, but at the same time, one of the most vulnerable parts of the ignition system. For that reason, the fact that said interrupters are rendered superfluous by the improved ignition system of this invention is one of the greatest technical advantages of the invention. Thereduction of weight simultaneously obtained in the ignition system according to this invention is an advantage not to be underestimated in a great many applications, such as, for example, in the field of aeronautics.

The principal object of the invention is to provide a method and apparatus forming a low voltage ignition system of the above mentioned kind. The apparatus in addition to the actual current generator, comprises the circuits in which said generator and one or more condensers are included, which condensers may be connected to the spark plugs at the moments and in the order desired by means of a form of distributor such as shown in applicants United States patent applications 792,985 now Patent No. 2,506,472, and 71,115 new Patent No. 2,587,780.

In the preferred form of'the invention, the method of supplying low voltage flush gap plugs consists in the steps of varying a magnetic field through a coil so that electrical energy is produced which, without voltage transformation, is applied to charge directly one or more condensers of a suitable capacity so that an impulse produced by one variation of the magneticfield charges the condenser to a level sufficient to produce a spark between the electrodes of a low voltage flush gap plug when connected to said condenser. Thus the condenser is gradually charged between two discharges, whereas when di- 2,711,495 Patented June 21, 1955 rectly connected to the spark plug the condenser discharges across said spark plug in a very rapid and powerful manner which is contrary to the usual high voltage ignition devices in which the energy produced by interrupting the primary circuit by means of an interrupter, is stepped up by transformation in the secondary circuit and directly supplied to the spark plug. In said previously known process the equipment undergoes very severe electrical and mechanical stresses, so that such equipment is one of the most vulnerable parts of an internal combustion engine. With the. proposed invention the drawbacks outlined above are readily avoided.

As indicated above, the apparatus for practicing the method of the invention comprises both the current generator and the charging circuit for the condenser. The generator may comprise means for producing'a magnetic flux in one or more coils as well as means to vary the magnetic flux in the coils. By varying the magnetic flux ditfering electromotive forces are induced in the coil or coils. The coil or coils are connected by a condenser charging circuit through one or more suitable current blocking or rectifying means to one or more condensers so that the condenser or condensers are charged by the voltage impulses produced by the electromotive forces in the coil or coils but cannot discharge back through the charging circuit. The current-blocking means may comprise for example rectifier tubes, stacks of rectifier'cells, mechanical rectifiers, spark gaps, or other known forms of current rectifying devices.

It may be desirable in some of the possible embodiments of the invention to use voltage limiting means to prevent overloading. This is especially important in embodiments in which the generator is driven by an internal combustion engine, such as an aircraft motor, and where due to an increase of the number of revolutions of the motor'the number of revolutions of the generator and consequently the-voltage supplied by it could become too high for the equipment.

The current generator for use with the systems of the invention may have several forms. In one form, a magnet may be used as a stator and with a rotatable armature having one or more coils. In another form, the magnet may be in the form of a rotatable armature whereas the stator is provided with one or more coils. In yet another form, a stationary magnet may be used, having an iron core rotating between the poles of the magnet and pole shoes of a stator having one or more coils, said iron core being shaped so that in certain rotatable positions of the core the magnetic flux of the magnet passes through the stator across the core. Obviously it is also possible to form the stator itself as a magnet, the magnetic circuit being closed and opened by the rotating core.

It is known that to increase the certainty of ignition by means of a low voltage fiush gap plug it is necessary that the condenser discharge across the spark plug occur as rapidly and powerfully as possible. Obviously this is only possible if actually the discharge is a true or substantially true aperiodic condenser discharge having a low resistance and a negligibly small inductance. According to this invention, this may easily be achieved with regard to the discharge circuit of the condenser inasmuch as the coils included in the charging circuit cannot aifect adversely the rapidity of the condenser discharge because of the interposed current blocking device or rectifier.

Preferred forms of the invention will be explained in more detail by reference to the following specification and drawings in which Figs. 1-9 are schematic wiring diagrams of various circuit arrangements of the invention, but for simplicity not showing the means of producing the varying magnetic field.

Fig. 10 is a diagrammatic view of a form of current generating device producing the varying magnetic field M and which may be used to advantage with any of the ignition circuits of Figs. 1 to 9 inclusive, and Figs. 11, 12 and 13 are views similar to Fig. but showing modified forms of current generator.

Referring to the drawings, in Fig. l the reference numeral 1 indicates the iron magnetic circuit, 2 and 3 the coils for a two phase alternator connected with a grounded or center-tapped zero point. Overvoltage protectors or spark discharge devices 4 and 5, protecting the system against voltage overloading may be connected in parallel to the coils 2 and 3, and the condenser 8 is connected parallel to both coils 2 and 3. Two current blocking or rectifying devices 6 and 7 are connected in series with these coils. As appears from the circuit arrangement, these coils 2 and 3 alternately charge the condenser. The connection to a distributor means 9 for determining the discharge moment of the condenser across the spark plug 49 is indicated at 9. Further it is advantageous to use the timing distributor disclosed in the applicants United States patent application 792,985, now Pat, No. 2,506,472, and 71,115, now Pat. No. 2,587,780.

In Fig. 2, the reference numeral 1 is the iron magnetic circuit and 3.0 the coil of a single phase alternator, one terminal of which is grounded. An overvoltage protector 11 is connected across coil ill for a purpose similar to that described in connection with Fig. 1. Two current limiting or rectifying means 12 and 13 may be connected in series with coil 1 Condensers 14 and 15 are connected in series with rectifying means 12 and 13, the connection being such that current flows from coil ill in opposite directions to condensers 14 and 15 respectively. This results in feeding two groups of spark plugs through two timing means 16 and 17 which may be similar to that indicated in Fig. l by reference numeral 9.

In Fig. 3, reference numeral 1 is the iron magnetic circuit and 18 and 19 the coils of a two phase alternator having four winding terminals and a grounded zero point. The coils l8 and 19, shunted if necessary by overvoltage protectors 2t and 21, supply current through limiting devices or rectifiers 22 and 23 to a condenser 8 which, in the same manner as indicated in Fig. l, is connected to the spark plug through connection 9.

In Fig. 4, reference numeral 1 is the iron magnetic circuit, 10' the coil of a single phase alternator feeding through two hot cathode valve rectifier tubes 24 and 25 passing the current in opposite directions respectively to two condensers 14 and 15, said condensers being connected to the spark plugs in a manner analogous to Fig. 2. An overvoltage protector 11 may bridge the coil 10.

In Fig. 5, again reference numeral 1 is the iron magnetic circuit and 16 the coil of a single phase alternator feeding the condenser 8 through a spark gap 26, said condenser being connected to the spark plug in a manner analogous to Fig. 1.

In Fig. 6, the reference numerals 1, l0, 8, 9 and 26 represent the same elements as previously described in Fig. 5, and a condenser 28 is connected across the terminals of the generator coil ll). The advantage of this condenser is that voltage oscillations occurring in the loading circuit, due to the bridging of the spark gap 26 by a spark, are limited to the circuit 128 and do not afiect adversely the working of the condenser 8.

Figs. 7 and 8 substmitialy correspond to Fig. 5, and 6, except, however, that a variable spark gap 27 is substituted for the spark gap 26.

In Fig. 9, the elements indicated by the numerals l, 2, 3, 8 and 9 correspond to those of Fig. 1 and are connected in the same manner. However, the condenser 8 is connected to the outer terminals of the coils through two cold cathode gas filled rectifier tubes 29 and 3t}.

In Fig. 10 of the drawings, one form of current generator for use in an ignition system according to this invention is shown. An iron core 30 corresponding in function to the iron magnetic circuit 1 of Fig. 1, for example, is provided with an alternator coil 31 corresponding to the coil 10 of Fig. l. The iron core 30 is provided with a gap 32 in which a rotor 33 formed of iron or other magnetically permeable material is rotatably positioned. North and south magnet poles 34 and 35 respectively are provided in the manner shown to produce a magnetic field and the rotor 33 is adapted to be rotated by the internal combusting engine or in any other suitable manner to provide a varying flux linkage from the magnet poles 34 and 35 through the iron core 30 and voltagev producing coil 31, as will be readily understood.

With reference to Fig. 11 of the drawings a modified form of current generator is shown in which the coil 38 is mounted on a rotatable armature 39 positioned in the gap of a magnetic stator 46 having north and south opposing poles as shown. The armature 39 may be rotated in any suitable manner such as by connection to the crankshaft of an internal combustion engine and the varying'magnetic flux thus induced in the armature 39 will generate current impulses in the coil 38. The ends of the coil 3% may, for example, be connected in the circuits described above through suitable commutator rings or the like (not shown).

In Fig. 12 of the drawings another modified form of a current generator is shown in which the coil 43 is mounted on an iron core 41 provided with an air gap.

A magnetic rotor 42 is rotatably positioned in said gap to provide a varying magnetic flux in said coil.

Fig. 13 represents a current generator comprising a magnetic core 44 provided with a coil 48 and having an air gap in which a rotor 47 formed of iron or other magnetically permeable material is rotatably positioned. The shape of said rotor is such that its rotation provides a varying flux linkage between the magnet poles 4S and 46 varying thereby the magnetic flux through the core 44 and the voltage producing coil 48, as will be readily understood.

In a general manner while in the above description there has been disclosed what is deemed to be practical and eficient embodiments of the invention, it should be well understood that the invention is not to be limited thereto as there might be changes made in the arrangemerit, disposition and form of the parts, or in the steps of the method, without departing from the principle of the present invention as comprehended within the scope of the accompanying claim.

I claim:

An ignition system for internal combustion engines utilizing at least one low voltage flush gap spark plug, comprising a coil, means inducing electromotive force in said coil, rectifying means, at least one ignition condenser, voltage limiting means preventing the overloading of the system, a discharge circuit for said ignition condenser, means electrically connecting said coil through said rectifying means to said ignition condenser, so as to block the discharge of the condenser through said coil to charge the condenser to a voltage not exceeding the peak voltage generated in said coil and to permit discharge of said ignition condenser only through said discharge circuit, said discharge circuit including means to provide a sub stantially non-inductive electrical connection between said ignition condenser and said spark plug, whereby said ignition system produces a substantially aperiodic spark discharge across the flush gap of said spark plug the voltage drop across said gap not exceeding the voltage to which the condenser has been previously charged.

References Cited in the file of this patent UNITED STATES PATENTS 791,856 Apple June 6, 1905 1,459,252 Plurnm July 26, 1923 1,537,903 Von Lepel May 12, 1925 1,892,371 Tuczek Dec. 27, 1932 2,003,466 Randolph et al. June 4, 1935 (Other references on following page) UNITED STATES PATENTS Randolph Jan. 14, 1936 Randolph et al. Feb. 11, 1936 Smits July 26, 1938 Hooven Nov. 21, 1939 Rabezzana et a1. Apr. 16, 1940 Schwarzmann et al. Oct. 15, 1942 6 Wall 'Nov. 4, 1947 Abend et a1 Aug. 24, 1948 Wargin et al. Dec. 14, 1948 Smits May 2, 1950 Henninger July 7, 1950 Tognola Oct. 16, 1951 

